Not Applicable
1. Field of the Invention
The present invention generally relates to the manufacture of solid state electrochemical cells, particularly high energy density cells having very thin electrode and electrolyte structures for building ultra-thin laminar batteries. The invention also relates to lithium polymer electrolyte batteries containing such electrochemical cells and to their methods of making.
2. Description of the Related Art
Lithium rechargeable batteries are the focus of intense investigation around the world because of the rapid proliferation of portable electronic devices in the international marketplace. The state-of-the-art lithium battery is a lithium ion battery which uses a carbon electrode as the negative electrode or anode and a lithiated metal oxide, such as lithiated cobalt oxide, lithiated nickel oxide, lithiated manganese oxide, or mixtures of these materials as the positive electrode or cathode, a microporous polypropylene or polyethylene separator that separates the two electrodes and prevents them from shorting electrically, and liquid organic solvents containing a lithium salt as the electrolyte. The electrolyte is usually absorbed into the separator material and provides high ionic conductivity (10xe2x88x92to 10xe2x88x922 S/cm) and migration of ions between the electrodes of the cell. These batteries are commercially available and are commonly used in portable computers, cellular telephones and camcorders among other applications. The specific energy and energy density of the lithium ion battery is usually about 125 Wh/kg and 260 Wh/l. Usually, the packaged battery (in a hard plastic case) has a much lower energy density than the:individual cell (20% lower). The cycle life (number of times the battery can be recharged) of this battery is about 500 to 800 cycles, the self-discharge (i.e. loss of capacity on standing) per month is about 10%, and cost is about $1 per Watt-hour of energy. These batteries can be manufactured at a high rate of speed. Even though this battery technology is being commercialized very heavily, there have been numerous safety questions. Cells that have been abused under crush test or high temperature test have been known to explode and catch fire.
An offshoot of the above system is the lithium ion polymer electrolyte battery. The electrode chemistry is the same, but the liquid electrolyte (up to 70% by weight of the electrolyte) in this case is absorbed in a polymer membrane instead of the microporous polypropylene separator. It is based on the Bellcore""s U.S. Pat. No. 5,296,318 utilizing a polyvinylidene fluoride (PVDF) polymer as the medium that absorbs the electrolyte solvent. Ironically, PVDF is non-conducting and so its sole function is to hold the liquid organic solvent(s) in its structure in a manner similar to a sponge holding water. Because the technology uses an electrolyte solvent absorbed in a polymer, it is not easy to manufacture cells in high speed. Automation of this technology may be very difficult. It is believed the energy densities (gravimetric and volumetric) for this type of battery are lower than the existing lithium ion batteries, cycle life is not too impressive, and cell cost is several dollars per Watt-hour. The physical forms the lithium ion polymer cell could take was a heavily touted feature, but today only flat prismatic cells are typically manufactured.
Another rechargeable lithium battery system uses a lithium metal as the negative electrode instead of carbon, and so the energy density of this system can be increased tremendously because of the very high specific capacity of metallic lithium compared to carbon. Gravimetric specific energy density as high as 200 to 250 Wh/kg have been reported in the literature for rechargeable lithium metal batteries. Lithium metal anode batteries are not new. Primary, non-rechargeable batteries using lithium metal, non-aqueous organic electrolytes and a positive electrode have been used in many applications for the past 25 years despite the fact that lithium metal is thermodynamically unstable in liquid organic solvents and reacts with the solvent irreversibly. Secondary batteries using lithium metal as the negative electrode, intercalation or insertion compounds as the positive electrode, and non-aqueous organic electrolytes were the focus of intense investigation during the 1970""s and 1980""s. However, the problem with using lithium in a rechargeable system is that because of the instability of lithium in these solvents, a large excess of lithium is required to off-set the chemical reaction of lithium with the solvent, usually as much as 3 to 5 fold. In addition, the cycle life of lithium metal batteries in organic solvent electrolytes is less than 200 cycles. Lithium plating and stripping during the charge and discharge cycles creates a porous deposit of very high surface area and increased activity of the lithium metal with respect to the electrolyte. The reaction is highly exothermic and the cell can vent with flame if heated or short-circuited. Much effort has been expended to improve the cycling efficiency of the lithium anode through changes to the electrolyte or investigating alloys of lower lithium reactivities. Safety features such as fusible separators which cease the electrochemical reactions when the battery temperature approaches a critical value and overcharge protection redox couples have also been incorporated to improve the safety of these cells.
In addition, liquid solvent electrolyte in any of the above cell systems is often corrosive and toxic and presents handling difficulties through spillage or leakage from the cell. It can also outgas during overcharge or overdischarge or at elevated temperatures, leading to safety problems. Most of the problems have been associated with the electrode/electrolyte interface.
In order to overcome the disadvantages inherent in liquid electrolytes and to obtain superior long-term storage stability there is interest in solid polymeric electrolytes in which ion mobility is achieved through coordination by sites on the polymer chain of electrolyte ions, thus promoting electrolyte dissolution and salt dissociation. An all-solid-state battery using an ionically conductive polymer membrane as the electrolyte would have several attractive features. It could be made into virtually any shape and size, be reasonably rugged and leakproof, and would have low self-discharge. It could be made into thin film power cells or thick film energy cells, would have high open-circuit potentials using a lithium anode, and could be produced by automated fabrication techniques. These features represent a unique combination of properties and give rise to the possibility of using such batteries, as either secondary or primary devices across a wide range of applications.
One polymer that has been examined extensively for use in a solid state battery is poly(ethylene oxide) or PEO, which is able to form stable complexes with a number of salts. Because of its low ionic conductivity at ambient temperature of about 10xe2x88x929 to 10xe2x88x928 S/cm, batteries examined using this material had to operate at 100xc2x0 C. and above. A major problem with PEO based electrolytes at temperatures below 60xc2x0 C. is their high crystallinity and the associated low ion mobility. In recent years a number of radically different approaches have been taken to improve the conductivity of PEO and PEO-based polymers that have also led to the proposal of other polymers. These approaches included, polymer modifications and synthesizing new polymers; forming composite polymers with ceramic materials; using plasticizer salts to increase the ion transport and mobility of the cation; using plasticizing solvents in the polymer again to increase the ionic character of the cation; among other approaches. Several review articles describe these approaches in detail, e.g. xe2x80x9cTechnology Assessment of Lithium Polymer Electrolyte Secondary Batteriesxe2x80x9d by M. Z. A. Munshi, Chapter 19 in Handbook of Solid State State Batteries and Capacitors, Ed. M. Z. A. Munshi (World Scientific Pub. Singapore) 1995; A. Hooper, M. Gauthier, and A. Belanger, in: xe2x80x9cElectrochemical Science and Technology of Polymersxe2x80x942, Ed. R. G. Linford (Elsevier Applied Science, London), 1987.
Polymer modification and synthesis of new polymers resulted in some improvement in the ionic conductivity but the mechanical property and integrity were poor. Probably, the best known polymer as a result of this synthesis is poly(bis(methoxyethoxyethoxide))-phosphazene, known as MEEP, which has an ionic conductivity of about 10xe2x88x925 S/cm at room temperature when combined with a lithium salt, but which has mechanical properties similar to glue. On the other hand, materials based on blocked copolymers may provide alternatives. For example, PEO-PPO-PEO crosslinked with trifunctional urethane and a lithium salt has an ionic conductivity of about 10xe2x88x925 S/cm but is too rigid, brittle and difficult to manufacture.
Inorganic conducting and non-conducting fillers have also been used to increase the ionic conductivity and mechanical property of the polymer. Addition of alpha alumina to (PEO)8.LiClO4 resulted in a negligible effect on the ionic conductivity but dramatically increased the mechanical property at 100xc2x0 C., while the addition of other ceramic materials such as ionically conductive beta alumina to PEO-NaI and PEO-LiClO4 complexes improved the ionic conductivity of PEO based electrolytes to about 10xe2x88x925 S/cm In another battery technology, inorganic fillers based on high surface area alumina and silica have been used to enhance the ionic conductivity of lithium iodide solid electrolyte from 10xe2x88x927 S/cm to 10xe2x88x925-10xe2x88x924 S/cm at room temperature (see C. C. Liang, J. Electrochemical Society, Vol. 120, page 1289 (1973)). Plasticizer salts based on lithium bis(trifluoromethane sulfonyl) imide, LiN(CF3SO2)2 trademarked as LiTFSI by Hydro-Quebec and distributed by the 3M Company under the product name, HQ-115 when added to PEO yields a conductivity of about 10xe2x88x925 S/cm.
None of the previous approaches toward improving polymer conductivity has resulted in adequate conductivity enhancements of the polymer electrolytes to permit room temperature operation of batteries utilizing the electrolyte. Accordingly, an attempt was made to increase the ionic conductivity of PEO-based polymer electrolyte by incorporating plasticizing solvents or low molecular weight polymers to the polymer electrolyte. The intent was to increase the ionic mobility and concentrations of the charge carriers in the solid polymer electrolyte by enhancing the dissociation of the lithium salt. Generally, it is believed that the lithium ion is also solvated to the solvent molecule and participates in enhancing the ionic mobility. Many electrolyte composites incorporating low molecular weight polymers or liquid organic solvents have been prepared and have demonstrated high conductivity at room temperature approaching conductivity values of the typical non-aqueous liquid electrolytes. For example, Kelly et al. (J Power Sources, 14:13 (1985)) demonstrate that adding 20 mole percent of liquid polyethylene glycol dimethyl ether polymer (PEGDME) to solid PEO polymer results in an increase in the ionic conductivity of the final plasticized polymer from 3xc3x9710xe2x88x927 S/cm to 10xe2x88x924 S/cm at 40xc2x0 C. However, the mechanical property of this material was very poor.
Bauer et al in U.S. Pat. No. 4,654,279 (1987) demonstrate that thermal crosslinking of polymers consisting of epoxies and methacrylates and plasticized with a solution of LiClO4 in a 400 MW PEG resulted in a conductivity of 4xc3x9710xe2x88x924 S/cm at 25xc2x0 C. This patent describes a polymeric electrolyte consisting of a two phase interpenetrating network (IPN) of a mechanically supporting phase of a continuous network of a cross-linked polymer and an ionically conducting phase comprising of a metal salt and a liquid polymer such as liquid PEG.
Many of these low molecular weight polymers have a relatively low dielectric constant when compared to their liquid solvent counterpart, and thus limit the number of charge carriers in the plasticized polymer. In an effort to overcome this hindrance, high dielectric constant liquid organic solvent such as ethylene carbonate (EC) and propylene carbonate (PC) have been incorporated in the host polymer both to increase the number of charge carriers and increase further the room temperature conductivity of the polymer. The use of these organic solvents to plasticize polymers such as poly(vinyl acetal), poly(acrylonitrile), poly(vinyl acetate) and hexafluoropropenevinylidene fluoride copolymer (Viton(trademark)) were made as early as 1975 by Feuillade and Perche (Journal of Applied Electrochemistry, Vol. 5, page 63 (1975)). However, the mechanical properties of these polymers were so poor that they had to be supported on porous matrices. Later Armand (Proc. Workshop on Li Non-Aqueous Battery Electrochemistry, The Electrochemical Soc. Vol. 80-7, page 261 (1980)) by crosslinking Viton(trademark) and plasticizing with a solution of 1M LiClO4 in PC produced a system with good room temperature conductivity (10xe2x88x924 S/cm) and good mechanical properties. Polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) were evaluated in the early 1980s and have also been doped with a variety of liquid polar solvents, yielding room temperature conductivities as high as 10xe2x88x923 S/cm. Subsequently, PVDF has been the subject of a recent patent from Bellcore (U.S. Pat. No. 5,296,318).
The use of PC in an ionically conductive matrix containing oxygen donor atoms such as PEO complexed with a lithium salt was first presented by the present inventor in a paper presented at the Fall Meeting of the Electrochemical Soc. held Oct. 18-23, 1987). Although room temperature battery performance data was presented at that time, the propylenecarbonate/lithium salt/polymer electrolyte did not have good mechanical properties. In the late 1980s through early 1990s, a series of U.S. patents including U.S. Pat. Nos. 4,792,504; 4,747,542; 4,792,504; 4,794,059; 4,808,496; 4,816,357; 4,830,939; 4,861,690; 4,925,751; 4,925,752; 4,935,317; 4,960,655; 4,990,413; 4,997,732; 5,006,431; 5,030,527; 5,057,385; 5,066,554 and European patents EP 0 359 524 and EP 0 411 949 were issued variously to MHB Inc. and Hope Industries. These patents described predominantly radiation curing methods for the preparation of interpenetrating polymeric networks containing various types of polyacrylates and liquid organic solvents. Although electron beam curing was the preferred method for polymerizing the IPN, thermal and ultraviolet curing methods were also proposed. The idea behind this was to contain the PC solution in the matrix of the polymeric network that would therefore yield a high ionic conductivity comparable to that of PC itself Indeed, this was demonstrated in typical polymeric networks, yielding conductivities of about 2xc3x9710xe2x88x923 S/cm at room temperature. An advantage with using electron beam curing compared to UV radiation is that an electron beam can penetrate through metallic components, and hence complete prototype cells can be made in-situ.
While the addition of organic plasticizers may help solve the problem of low ionic conductivity in polymer electrolytes, they necessarily introduce additional electrolyte components that may have deleterious effects on other electrolyte properties, such as stability in contact with metallic lithium. Like the liquid organic electrolytes, plasticized polymer electrolyte is not thermodynamically stable at the lithium metal potential. In addition, polymer electrolytes based on such designs cannot be manufactured in very thin film form so as to reduce their overall resistance and hence cell resistance, since the polymer will not have the sufficient strength to hold the liquid organic solvents in its matrix. For such a system to be fully functional it must be based on a thick film concept, which increases its overall cell resistance and reduces the energy density due to a reduction in the active components in the cell. Another problem with this type of design is the fact that polymers containing liquids cannot be wound along with the rest of the electrode components in a winding machine, since the liquid will tend to ooze out of the polymer as soon as any stress is applied to the polymer.
Advanced commercial battery technologies such as the lithium ion (Sony type), THINFILM(trademark) lead-acid (Bolder Battery Co.), and nickel-metal hydride batteries do not demonstrate very high cycle life, i.e., several tens of thousands of cycles. This is due primarily to considerable phase changes and composite structure segregation that take place within the electrode, inefficient materials utilization and particle movements, and expansion and contraction during charge and discharge. However, batteries such as these do represent a breakthrough in the design of lithium ion batteries and yielded higher cycle life than was previously available by their use of relatively thin electrode structures. The THINFILM(trademark) lead-acid battery for high power applications is a good example of thin electrode structures and good materials utilization, but the electrode is still not thin enough to achieve a cycle life of several thousand. Hence, a major drawback of these batteries is that the liquid electrolytes necessarily limit their cycle life.
Lithium primary battery electrodes are traditionally made by calendering the cathode paste onto a nickel or stainless steel gauze substrate material and compacting between heated rollers. In the case of lithium metal anodes the gauze is used as a substrate material. The substrate material is usually about 2 to 3 mils thick while the anode and cathode are typically about 5 to 10 mils thick The anode and cathode are sandwiched with a microporous polypropylene separator between them and wound in a jelly-roll manner. Usually, the laminates are very thick and the electrode length is about two feet in a typical AA size cell. Rechargeable lithium metal anode batteries, which were available a few years ago, were also constructed in this manner.
These techniques have changed considerably with the advent of lithium ion battery construction. In lithium ion batteries the carbon anode is pasted in relatively thin film form onto a copper foil electrode and the lithiated metal oxide cathode is pasted onto an aluminum foil. The substrate thickness for both anode and cathode is in a range from about 25 to 35 microns, and the active electrode is about 25 microns thick. Additionally, the length of each electrode in a typical AA size cell is about twice that of lithium anode cells. Present day electrode/electrolyte component thickness in gelled electrolyte lithium ion cells is of the order of 50 to 75 microns each. This remains far too thick for optimum electrode utilization and high rate capability. Metallic current collectors are also used, not only adding weight but unwanted thickness to the battery. The thick electrode concept in commercial cells is designed for maximum capacity, while the thick gelled PVDF electrolyte provides ease of handling. However, the internal resistance of this battery is still relatively higher than its liquid electrolyte counterpart, thus decreasing battery performance. Cells constructed from such a design cannot be used at high discharge and charge rates. Thick inactive substrates used in such cell construction effectively reduce the energy density of the battery. In addition, this design exposes the cells to risk of high polarization during charge and discharge, which could lead to breakdown of the liquid solvent electrolyte and consequently loss of capacity, loss of cycle life and inadequate safety.
On the other hand, an existing lead acid battery designed for an electric car can only provide about 60 to 80 miles range before recharge is not suitable either. Known lithium ion batteries are neither cost-effective nor safe for electric vehicles. Furthermore, consumers are generally unwilling to pay a premium price for an electric vehicle while gasoline vehicles remain far less expensive to operate. However, if the price of the battery can be reduced, and the mileage range of the electric vehicle can be increased to a value closer to the mileage range of a conventional vehicle, the electric vehicle will become quite feasible for widespread use.
Another problem with existing rechargeable batteries, even those used in small electronic devices, is that they contain liquid organic solvents that have been found to be relatively unsafe for consumer use. Also, there have been many reports of safety problems with lithium ion batteries, in particular, containing organic solvents as the electrolyte in portable electronics devices. The lithium ion batteries must have special charging circuitry since the battery cannot tolerate any amount of overcharge. Also, they have no built-in chemical mechanism, such as that in nickel-cadmium batteries, that provides for recombination reactions to take over when cells reach full charge, so that the electrolyte never decomposes. In liquid organic electrolyte cells, there is no recombination mechanism and the cell electrolyte quickly start to decompose with overvoltage, leading to production of unwanted gaseous species.
Much of the literature in this field reports that polymer electrolyte batteries can be made in very thin film form and can be flexible. However, batteries containing the polymer electrolytes with liquid organic solvents actually tend to lose performance over time, primarily because of cell orientation related problems. A battery standing upright will tend to have the liquid solvents travel to the bottom of the cell, and during charge and discharge, the current along the cell height will be different because of the difference in the conductivity at the bottom of the electrode and at the top. Such cells do not have very high cycle life and lose capacity as a result of poor charging and discharging.
Glassy electrolytes based on the ternary system, LiIxe2x80x94Li2Sxe2x80x94P2S5 and LiIxe2x80x94Li2Sxe2x80x94B2S3 exhibit lithium ion conductivities of about 1xc3x9710xe2x88x923 S/cm and 2xc3x9710xe2x88x923 S/cm at room temperature, respectively, for bulk electrolytes. Since the electrolyte is very hard and brittle, it is usually used in a vapor deposited form in very thin films so as to achieve a continuous uniform thickness. Lithium anode batteries based on thin film glassy electrolytes with electrolyte thickness of one to several microns have demonstrated current densities of several tens to hundreds of microamperes per square centimeter at room temperature. Unfortunately, the fabrication of these batteries requires extremely sophisticated deposition equipment and production feasibility and performance of large cells have not yet been demonstrated.
All of the prior art techniques that have been employed to improve the ionic conductivity, mechanical strength, safety, and chemical stability, and to reduce cost by simplifying or improving the synthesis of polymer electrolytes have one or more serious shortcomings. As a result, there is still no room temperature conducting polymer electrolyte available today that is entirely suitable for use with a lithium metal anode in a rechargeable lithium battery, for example. There remains a need for electrochemical cells with polymer electrolytes that have good ionic conductivity at room temperature and below, so that the performance of an electrochemical cell at room temperature or below can be improved. There is also a great need for thinner component batteries that avoid the use of organic solvents in the electrolyte without sacrificing energy density.
The electrochemical cells and batteries of the present invention overcome many of the kinetic constraints on the specific power, cycling efficiency and capacity utilization that are typical of electrochemical devices employing conventional polymer electrolytes and electrodes. A kinetic constraint is, for example, the inability to discharge at high rates leading to polarization losses. The lithium solid polymer electrolytes employed in the cells and batteries of certain preferred embodiments of the present invention are suitable for use at room temperature, and even below, due to their high ionic conductivity compared to previous lithium polymer electrolytes. Not only are these new electrolytes highly conductive, they are also strong enough to be manufactured by high speed roll-to-roll techniques. One advantage of the preferred anodes, cathodes, electrodes and half-electrodes, bipolar units, electrochemical cells and batteries of the present invention is that they employ a thermodynamically stable dry polymer electrolyte that can be manufactured using high speed extrusion or deposition techniques.
While the secondary behavior of existing lithium batteries has been limited by a number of factors related to the materials and design of the system, the preferred ultra-thin battery embodiments of the present invention overcome those drawbacks by incorporating very thin electrode and electrolyte structures, based on ultra thin film active and inactive components in long lengths. This effectively increases the surface area of the active plates. As a consequence, these new batteries have a higher current drain capability lower resistance, higher energy content, lower self-discharge rate, and a wider operating temperature range than presently available solid state batteries. Among many features and advantages, the new rechargeable batteries also provide freedom from dendrite formation, higher efficiency, lower internal resistance, greater capacity utilization, higher cycle life or cyclability, and better reliability and safety than previously available in a rechargeable metal ion battery. Moreover, these batteries are better able to tolerate overcharge and will not lead to the emission of deleterious species or outgassing. In addition, the wholly solid-state lithium-based systems of preferred embodiments of the present invention use less lithium in the cell than is typically used in existing lithium cells, thereby reducing cost as well as increasing the energy content.
In accordance with a preferred embodiment of the present invention, an all-solid-state laminar electrochemical cell for a battery is provided. The cell comprises an anode layer about 0.1-100xcexc thick, a cathode layer about 0.1-100xcexc thick, an anode current collector about 0.5-50xcexc thick attached to said anode, a cathode current collector about 0.5-50xcexc attached to the cathode, and a layer of solid polymer electrolyte disposed between the anode and cathode layers.
In an alternative embodiment, a all-solid-state laminar electrochemical cell includes an anode layer, a cathode layer, an anode current collector attached to said anode, a cathode current collector attached to the cathode, and a layer of solid polymer electrolyte disposed between the anode and cathode layers. The solid polymer electrolyte is a cationic conductor and has a conductivity of at least 10xe2x88x924 S/cm at 25xc2x0 C. and comprises a mixture of a base polymer material comprising at least one ionically conductive polymer and having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a metal salt. The electrolyte mixture also includes a metal salt, an inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and an ionic conducting material having an average particle size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C. In certain very thin embodiments of the electrochemical cell the anode layer is about 0.1-100xcexc thick, the cathode layer is about 0.1-100xcexc thick, the anode and cathode current collectors are each 0.5-50xcexc thick, and the solid polymer electrolyte is about 0.5-100xcexc thick. Preferably the anode is lithium, and the metal salt is a lithium salt, such as lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium tetrachloroaluminate (LiAlCl4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium methide (LiC(SO2CF3)3 and lithium bis(trifluoromethane sulfonyl) imide (LiN(CF3SO2)2). It is preferred that the ionic conducting material of the solid polymer electrolyte is a lithium ion conducting material such as a glassy lithium ion conductor or a ceramic lithium ion conductor. It is also preferred that the inorganic filled is fumed silica and alumina.
In some embodiments of the electrochemical cells the base polymer material comprises at least two polymers, and in some of those embodiments the base polymer material comprises about 1% to 99% (by weight of said base polymer material) of one polymer and the remainder is at least one other polymer. In the preferred embodiments the first polymer is an ionically conductive polymer, the monomers of which have a hetero atom with a lone pair of electrons available for the metal ions of a metal salt to attach to and move between during conduction, when the first polymer is mixed with a metal salt. The first polymer may be a linear polymer, random copolymer, block copolymer, comb-branched block copolymer, network structure, single ion conductor, polyvinylidene fluoride or chloride (or a copolymer of their derivatives), poly(chlorotrifluoroethylene), poly(ethylene-chlorotrifluoro-ethylene) or poly(fluorinated ethylene-propylene). In some embodiments, the first polymer is combinable with a lithium salt such that the ionic conductivity of the polymer is enhanced, and the polymer is chosen from the group consisting of polyethylene oxide (PEO), oxymethylene linked PEO, PEO-PPO-PEO crosslinked with trifunctional urethane; poly(bis(methoxy-ethoxy-ethoxide))-phosphazene (MEEP); a triol-type PEO crosslinked with difunctional urethane, poly((oligo)oxyethylene)methacrylate-co-alkali metal methacrylate; polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polymethylacrylonitrile (PMAN); polysiloxanes and their copolymers and derivatives, polyvinylidene fluoride or chloride and copolymers of their derivatives, poly(chlorotrifluoro-ethylene), poly(ethylene-chlorotrifluoroethylene), poly(fluorinated ethylene-propylene), acrylate-based polymer, other similar solvent-free polymers, combinations of the foregoing polymers either condensed or crosslinked to form a different polymer, and physical mixtures of any of these polymers.
In some embodiments of the all-solid-state laminar electrochemical cell a second polymer of the at least two polymers making up the base polymer material is more inert with respect to ionic conductivity and is stronger than the first polymer. The conductivity is measured when each of the polymers is in the form of a thin film. The second polymer may be chosen from the group consisting of polyester (PET), polypropylene (PP), polyethylene napthalate (PEN), polyvinylidene fluoride (PVDF), polycarbonate (PC), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), and other polymer materials that possess stability and strength characteristics similar to one of said group of polymers.
Some embodiments of the all-solid-state laminar electrochemical cells have a stacked configuration, or the layers may be wound or rolled together. Some of the more preferred electrochemical cells have conformable structures, due to their flexibility and thinness.
In some embodiments the current collectors used in the electrochemical cell are very thin structures that are either a metallic element less than 10xcexc thick or a metallized plastic 0.5 to 50xcexc thick.
Also provided in accordance with the present invention are elemental anodes for a polymer electrolyte battery. In some embodiments the anode comprises a 0.1-100xcexc thick layer of elemental anode material overlying a current collector that is either a metallic current collector about 0.5-50xcexc thick, or a metallized polymer current collector comprising a polymer substrate about 0.5-50xcexc thick and a metallization layer up to about 1xcexc thick overlying the polymer substrate. The metallic current collector and the metallization layer are preferably aluminum, nickel, carbon, inconel, copper, stainless steel, zinc and gold or other suitably compatible materials with the active electrode.
In some embodiments the metallic current collector is about 2-5xcexc in thickness, and in some embodiments it is less than 2xcexc thick. In the embodiments employing a metallized polymer current collector, it may comprise a polymer substrate about 0.5-50xcexc thick and a metallization layer up to 1xcexc thick on top of the polymer substrate. Certain preferred embodiments leave a non-metallized margin on the polymer substrate. In preferred embodiments of the elemental anode, the anode material is chosen from the group consisting of lithium, sodium, potassium, magnesium, calcium, zinc, nickel, ion-insertion polymers, ion-insertion inorganic electrodes, carbon and tin oxide.
Also in accordance with the present invention anode half-elements for polymer electrolyte batteries are provided. In some embodiments the anode half-element includes one of the above-described elemental anodes together with a layer of solid polymer electrolyte overlying the elemental anode material. The solid polymer electrolyte is a cationic conductor having a conductivity greater than 1xc3x9710xe2x88x924 S/cm at 25xc2x0 C. or below. The solid polymer electrolyte comprises a mixture of base polymer material, a metal salt, inorganic filler and ionic conducting material as described above.
In some embodiments the anode half-element is for a lithium polymer electrolyte battery and comprises a substrate about 0.5-50xcexc thick containing a current collector. A thin layer of lithium anode material about 0.1-100xcexc thick lies on top of the current collector. The lithium anode material may comprise a mixture of an active anode substance and a base polymer material comprising at least one ionically conductive polymer and having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a lithium salt. The mixture also include the lithium salt, an inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and a lithium ion conducting material having an average particle size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C. In some of these embodiments the active anode substance is chosen from the group consisting of ion-insertion polymers, ion-insertion inorganic electrodes, carbon insertion electrodes and tin oxide.
Further provided by the present invention are cathode half elements for solid polymer electrolyte batteries. In some embodiments the cathode half element comprises a 0.1-100xcexc thick layer of cathode material overlying a current collector chosen from the group consisting of metallic current collectors about 0.5-50xcexc thick, and metallized polymer current collectors about 0.5-50xcexc thick comprising a polymer substrate and a metallization layer up to about 1xcexc thick.
In some of these embodiments the cathode material comprises a mixture of an active cathode substance, such as an oxide, sulfide or selenide, and a solid polymer electrolyte composition as described above. The active cathode substance may be one chosen from the group consisting of MnO2, LiMn2O4, LixMnO2, MoS2, MoS3, MoV2O8, CoO2, LixCoO2, V6O13, V2O5, V3O8, VO2, V2S5, TiS2, NbSe3, Cr2O5, Cr3O8, WO3, LixNiO2, LixNiyCozO2, LixMnzO2 and LixCoyMnzO2.
In some alternative embodiments the cathode half element may employ as the active cathode substance a lithium doped electronically conducting polymer. The electronically conducting polymer may be polypyrrole, polyaniline or polyacetylene, for example.
Further provided by the present invention are thin electrodes for an all-solid-state lithium polymer electrolyte battery comprising a substrate about 0.5-50xcexc thick, current collector, and a layer of active electrode/polymer electrolyte composite about 0.1-100xcexc thick overlying a side of the substrate. The active electrode/polymer electrolyte composite comprises a mixture of an active electrode material, a base polymer material comprising at least one ionically conductive polymer and having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a lithium salt, a lithium salt, an inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and an ionic conducting material having an average particle size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C. In some embodiments the substrate is an ultra-thin film metallized polymer substrate comprising a polymer layer about 0.5-50 microns thick and a metallization layer up to 1xcexc thick and having a conductivity of about 0.01-1.0 ohm per square. The metallization layer covers one side of the polymer layer and serves as the current collector. The metallization layer is 0.0xcexc thick or less in some of the preferred embodiments.
Also in accordance with the present invention are provided bipolar electrodes for a battery. Certain embodiments of the bipolar electrodes comprise a flexible polymer substrate about 0.5-50xcexc thick and having two opposite sides and two opposite edges. In some embodiments of the bipolar electrode the flexible polymer substrate is impregnated with an electronically conductive element that is chemically inert to said anode and cathode layers. Two metallization layers 0.01-1xcexc thick overlie each entire sides of the polymer substrate with no margins. A 0.1-100xcexc thick anode layer overlies one of the metallization layers and a 0.1-100xcexc thick cathode layer overlies the other metallization layer. The ration of the substrate thickness to anode or cathode layer thickness is less than about 0.5, and the surface resistivity of the anode and cathode layers is each less than 0.1 ohms per square. Some embodiments of the bipolar electrode include a layer of solid polymer electrolyte overlying the anode and/or the cathode. The solid polymer electrolyte comprises a mixture of base polymer material, metal sat, inorganic filler and ionic conducting material as previously described.
A preferred embodiment of a bipolar electrode for a battery comprises a flexible polymer substrate about 0.5-50xcexc thick impregnated with an electronically conductive element. Two metallization layers up to 1xcexc thick overlie respective opposite sides of the polymer substrate. A 0.1-100xcexc thick anode layer overlies one metallization layer and a 0.1-100xcexc thick cathode layer overlies the other metallization layer. The electronically conductive element is chemically inert to the anode and cathode and preferably has a conductivity greater than 102 S/cm at 25xc2x0 C. In certain embodiments the electronically conductive element is chosen from the group consisting of conductive carbon, electronically conducting polymer, e.g. polyacetylene, polypyrrole, polyaniline, etc., and finely divided metal.
Still further provided by the present invention are batteries employing the above described electrodes, half-elements and electrochemical cells. One such embodiment is a defined capacity battery in which the anode layer comprises a predetermined deposited amount lithium, sodium, potassium, magnesium, calcium, zinc or nickel per unit area of said anode layer.
Certain embodiments of the invention provide leakproof batteries comprising an all-solid-state laminar electrochemical cell as described above together with a hermetically sealed covering.
Certain embodiments provide overcharge tolerant batteries comprising an all-solid-state laminar electrochemical cell as described above. An overcharge tolerant battery may also include an overcharge indicator.
Orientation tolerant polymer electrolyte batteries having an all-solid-state composition employing the above described laminar electrochemical cells are also provided by the present invention and operate optimally in any configuration or independent of vertical or horizontal positioning. In certain preferred embodiments the battery employs a wound electrochemical cell in a cylindrical configuration. Metallic terminations may be applied to the cylinder ends. The terminations may comprise one or more end coatings. Some embodiments also include a hermetic or moisture-resistant covering, such as an epoxy coating, to protect the cell from the environment. Instead of containing a wound electrochemical cell, some embodiments of the all-solid-state batteries contain a laminar cell in a zig-zag or concertina configuration.
A preferred embodiment of a battery is an all-solid-state lithium polymer electrolyte battery comprising a pair of spaced-apart flexible thin film electrodes, each of the electrodes comprising a layer of active electrode material overlying a polymer substrate having an adherent electrically conductive layer disposed thereon and/or having an electrically conductive material dispersed in the polymer substrate. The battery also includes a resilient and flexible thin film solid polymer electrolyte tightly disposed between the pair of electrodes, said electrolyte having a conductivity of at least about 1xc3x9710xe2x88x924 S/cm at 25xc2x0 C. and containing a mixture of at least two polymers, one of which is an ionically conductive polymer having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a lithium salt. The mixture also contains the lithium salt, an inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and a lithium ion conducting material having an average article size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C. In certain embodiments the inactive polymer substrate of each electrode is PET, PP, PPS, PEN, PVDF or PE. In certain embodiments the inactive polymer substrate is a metallized polymer substrate having a thin metallization layer which serves as the adherent electrically conductive layer. In some preferred embodiments the metallized polymer substrate is about 0.5 to 50 microns thick and the thin metallization layer has a resistivity of about 0.01 to 1 ohm per square. The metallized polymer substrate may further include a first side containing a first non-metallized margin. The battery of claim 56 wherein said non-metallized margin extends about 1 to 3 mm from an edge of said first side to an edge of said first metallization layer. Some embodiments also comprise a second metallization layer adhered to a second side of the polymer layer. In these embodiments the second side of the polymer layer comprises a second unmetallized margin directly opposite the first unmetallized margin and extending about 1 to 3 mm from the substrate edge to an edge of the second metallization layer.
Also in accordance with the present invention are provided improved lithium polymer electrolyte batteries. One embodiment of an improved battery having a lithium metal anode layer, a cathode layer, an anode current collector attached to said anode layer, a cathode current collector attached to said cathode layer, and a layer of lithium polymer electrolyte disposed between said anode and cathode layers, includes the improvement comprising substitution of a lithium solid polymer electrolyte having a conductivity of at least about 10xe2x88x923 to 10xe2x88x924 S/cm at 25xc2x0 C. for the polymer electrolyte. The lithium solid polymer electrolyte comprises a mixture of a polymer or polymer blend having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a lithium salt. The mixture also includes the lithium salt, an inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and a lithium ion conducting material having an average particle size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C. The improved battery has a cell resistance less than or equal to that of a liquid electrolyte lithium battery.
Certain of the improved lithium polymer batteries substitute an ultra-thin current collector that is either a metallic element less than 10xcexc thick or a metallized plastic 0.5 to 50xcexc thick, in place of a conventional current collector.
In some embodiments of an improved lithium polymer battery, the improvement also includes substituting for the anode and/or cathode layers a flexible ultra thin film electrode containing a metallized polymer substrate having an inactive polymer layer about 0.5-50 microns thick, a metallization layer up to about 0.01 micron thick overlying the inactive polymer layer. The improvement also includes a layer of active electrode material up to about 5 microns thick overlying the metallization layer, and substituting for the polymeric electrolyte a lithium solid polymer electrolyte in the form of a thin film up to about 5 microns thick. The lithium solid polymer electrolyte comprises a mixture of a polymer or polymer blend having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a lithium salt, the lithium salt, an inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and a lithium ion conducting material having an average particle size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C.
In some embodiments of the improved batteries, the inorganic filler is 0.1-20% (by volume of solid polymer electrolyte) high surface area filler having an average particle size xe2x89xa60.01 micron and chosen from the group consisting of fumed silica and alumina.
In some embodiments of the improved batteries the lithium ion conductor material is 0.1-80% sulfide glass (by volume of solid polymer electrolyte).
In some embodiments of the improved batteries the lithium ion conductor material is a ceramic ion conductor chosen from the group consisting of lithium beta alumina and silicates.
In certain embodiments of an improved lithium polymer electrolyte battery the cathode layer comprises a solid polymeric composite containing a mixture of active cathode material having an average particle size xe2x89xa60.1 micron and a base polymer material comprising at least one ionically conductive polymer and having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a metal salt. The mixture also includes a metal salt, an inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and an ionic conducting material having an average particle size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C. In some embodiments the composite cathode may also contain an appropriate binder material.
A preferred embodiment of a battery of the invention is a rechargeable all-solid-state lithium polymer electrolyte battery comprising an ultra thin lithium anode, which may be either a metallic lithium element or a lithium metal layer about 0.1 to 100 microns thick, over the metallization layer of a metallized polymer substrate. The metallized polymer substrate has an inactive polymer layer about 0.5 to 50 microns thick and a metallization layer 0.01-1xcexc thick on top of the inactive polymer layer. This battery also has an ultra thin-film cathode layer containing a metallized polymer substrate. The metallized polymer substrate has an inactive polymer layer about 0.5 to 50 microns thick and a metallization layer about 0.01-1xcexc thick on top of the inactive polymer layer, and has a layer of active cathode material 0.1-100xcexc thick on top of the metallization layer. The battery also has a polymer electrolyte layer up to 0.2-100xcexc thick placed between the above-described anode and cathode layers. This polymer electrolyte has a conductivity greater than 1xc3x9710xe2x88x924 S/cm at 25xc2x0 C., or may even conduct as well below 25xc2x0 C. The polymer electrolyte comprises a mixture of a base polymer material comprising at least one ionically conductive polymer and having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a lithium salt. The mixture also includes the lithium salt, an inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and a lithium ion conducting material having an average particle size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C.
In certain preferred embodiments of a rechargeable all-solid-state lithium polymer electrolyte battery, as described above, the polymer electrolyte comprises a mixture of about 30 to 95% (by weight of solid polymer electrolyte) base polymer material containing at least one ionically conductive polymer and having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a lithium salt. The mixture also includes about 1 to 25% (by weight of solid polymer electrolyte) said lithium salt, about 0.1-60% (by volume of solid polymer electrolyte) inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and about 0.1-80% (by volume of solid polymer electrolyte) ionic conducting material having an average particle size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C. In certain preferred embodiments the concentration of inorganic filler is about 0.1-20% (by volume of solid polymer electrolyte) and the concentration of ionic conducting material is about 0.1-20% (by volume of solid polymer electrolyte).
Also in accordance with the present invention are provided methods of making ultra-thin solid polymer electrochemical cells, and thin components thereof. In one embodiment, an ultra-thin solid polymer electrochemical cell is fabricated by a) preparing an anode sheet by applying active anode material to an inactive anode substrate such that the ratio of anode substrate thickness to anode sheet thickness is xe2x89xa60.8 and the conductivity is xe2x89xa61 ohms per square; b) preparing a cathode sheet by applying active cathode material to an inactive cathode substrate such that the ratio of cathode substrate thickness to cathode sheet thickness is xe2x89xa60.8 and the conductivity is xe2x89xa61 ohms per square; c) preparing a solid polymer electrolyte having a conductivity of at least 10xe2x88x924 S/cm at 25xc2x0 C. and comprising a mixture of a polymer or polymer blend having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a lithium salt, the lithium salt, an inorganic filler having an average particle size  less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and a lithium ion conducting material having an average particle size  less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C., an organic solvent, and a curing agent; d) coating the cathode sheet with the solid polymer electrolyte, e) evaporating the solvent, and f) curing the polymer electrolyte to yield an electrolyte-coated cathode sheet; g) laminating the electrolyte-coated cathode sheet and the anode sheet together such that the electrolyte coat is between the cathode active material and the anode active material, whereby a cathode/electrolyte/anode laminate is formed; h) optionally winding the laminate; and i) optionally shaping the laminate.
In some embodiments the step of preparing an anode sheet comprises applying active anode material-to an inactive anode substrate containing an inactive polymer substrate and a thin metallization layer overlying at least a portion of the polymer substrate. The application is done is such a manner that the ratio of anode substrate thickness to anode sheet thickness is xe2x89xa60.8 and the conductivity is xe2x89xa61 ohms per square. The step of preparing a cathode sheet comprises applying active cathode material to an inactive cathode substrate containing an inactive polymer substrate and a thin metallization layer overlying at least a portion of the polymer substrate, such that the ratio of cathode substrate thickness to cathode sheet thickness is also xe2x89xa60.8 and the conductivity is xe2x89xa61 ohms per square.
Methods of making a strong and flexible anode/electrolyte half-element for a laminar battery are provided according to certain embodiments of the present invention. In some of these embodiments the method includes depositing a 0.1-100 microns thick layer of elemental metal onto an electrically conductive substrate that is either a metallic current collector about 1-10xcexc thick or a metallized polymer current collector comprising a polymer substrate about 0.5-50xcexc thick and a metallization layer up to about 1xcexc thick on top of the polymer substrate. The elemental metal is preferably lithium, sodium, potassium, magnesium, calcium, zinc or nickel. The metallization layer preferably has a resistivity less than 1 ohms per square. The metallization-material is chosen from the group consisting of Al, Cu, Ni, Zn, C, stainless steel, iconel, or any other suitably compatible material with the active electrode. The process also includes applying a layer of solid polymer electrolyte onto the layer of elemental metal, the solid polymer electrolyte having a conductivity greater than 1xc3x9710xe2x88x924 S/cm at 25xc2x0 C. or below. The electrolyte comprises a mixture of base polymer material, metal salt, inorganic filler and ionic conducting material, as previously described. In certain embodiments elemental metal depositing comprises evaporating or sputtering the metal directly onto the current collector in a continuous step, and in some embodiments a predetermined quantity of elemental metal is applied to yield a precise elemental metal capacity per unit area of anode when the anode half-element is employed in a defined-capacity battery. The method may also include tabbing the elemental metal layer by metal punching through the polymer substrate.
Methods of making a strong and flexible electrode/electrolyte half-element for a laminar battery are also provided according to certain embodiments of the present invention. In some of these embodiments the method comprises depositing a 0.1-100 microns thick layer of active anode or cathode material onto an electrically conductive substrate containing either a metallic current collector about 1-10xcexc thick or a metallized polymer current collector comprising a polymer substrate about 0.5-50xcexc thick and a metallization layer up to about 1xcexc thick overlying the polymer substrate. The metallization layer has a resistivity less than 1 ohm per square. The method also includes applying a layer of solid polymer electrolyte onto the layer of cathode material. The solid polymer electrolyte can be the same as described above. In certain embodiments of this method depositing of the active electrode material includes casting the active electrode material using a knife coater, doctor blade coater, wire-wound bar coater, air knife coater, squeeze roll, gravure coater, reverse roll coater, cast film coater or a transfer roll coater. The solid polymer electrolyte may also be applied over the electrode material by one of the same casting techniques. In other embodiments the depositing of active electrode material and application of solid polymer electrolyte may be accomplished by extrusion.
Still further, methods of making a thin bipolar battery are provided according to certain embodiments of the present invention. In some of these embodiments the method comprises laminating tightly together at least one layer of bipolar unit between a layer of first anode and a layer of first cathode to provide a stack having laminar ends. A preferred bipolar unit includes a flexible first polymer substrate about 1-10xcexc thick that has two opposite sides, for example, like the top and bottom of a flat, rectangular or elongated sheet. The substrate also has two opposite edges, for example, like the longitudinal edges of an elongated flat sheet. The first polymer substrate optionally includes an electrically conductive material dispersed in the polymer substrate. Two metallization layers up to 1xcexc thick coat each said side. The bipolar unit also includes a 0.1-100xcexc thick second anode layer overlying one metallization layer, and a 0.1-100xcexc thick second cathode layer overlying the other said metallization layer. In preferred embodiments, the ratio of substrate thickness to second anode or second cathode layer thickness is less than about 0.5, and the surface resistivity of the second anode and second cathode layer is less than 1 ohms per square. This bipolar unit also includes a layer of solid polymer electrolyte overlying at least one of the second anode and the second cathode. The solid polymer electrolyte having a conductivity of at least 10xe2x88x924 S/cm at 25xc2x0 C. and comprising an above-described mixture. The first anode comprises a 0.1-100xcexc thick layer of elemental anode material overlying a current collector that is either a metallic current collector about 1-10xcexc thick or a metallized polymer current collector comprising a second polymer substrate about 0.5-50xcexc thick and a metallization layer up to about 1xcexc thick overlying the second substrate. This embodiment of a bipolar unit also includes a layer of the solid polymer electrolyte overlying the layer of elemental anode material. The first cathode comprises a 0.1-100xcexc thick layer of cathode material overlying a current collector that is either a metallic current collector about 1-10xcexc thick or a metallized polymer current collector about 0.5-50xcexc thick comprising a polymer substrate and a metallization layer up to about 1xcexc thick. In making up the bipolar battery, the first anode and first cathode are oriented such that the first anode elemental material opposes the active cathode substance of the second cathode of a bipolar unit, with a layer of solid polymer electrolyte disposed between the first anode and second cathode. The process of making the battery also includes applying current collectors to the laminar ends.
In yet another embodiment of the present invention, methods of manufacturing ultra-thin laminar batteries are provided. According to some of these embodiments the method comprises a) winding a 0.1-100xcexc thick cathode sheet into a roll, the cathode sheet comprising a flexible inactive polymer substrate and a layer of active cathode material overlying the substrate; b) extruding a uniform 1-10xcexc thick layer of a lithium solid polymer electrolyte composition onto the cathode sheet while the roll is drawn at a uniform rate by an uptake reel, to obtain a roll of flexible substrate/active cathode/electrolyte composite, said lithium solid polymer electrolyte comprising a mixture of a base polymer material comprising at least one ionically conductive polymer and having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with a lithium salt. The mixture also includes the lithium salt, inorganic filler and a lithium ion conducting material, as previously described; c) curing the extruded polymer electrolyte composition as the composite is continuously wound by said uptake reel, to yield a roll of cathode/electrolyte laminate; d) winding a lithium anode sheet to provide a roll of anode laminate, said lithium anode sheet comprising a 0.1-100xcexc thick layer of elemental anode material overlying a current collector that is either a metallic current collectors about 1xc3x9710xcexc thick or a metallized polymer current collector comprising a polymer substrate about 0.5-50xcexc thick and a metallization layer up to about 1 thick overlying the polymer substrate; e) winding a 0.5-100xcexc thick sheet of inert plastic to provide a first roll of plastic; f) winding a 0.5-100xcexc thick sheet of inert plastic to provide a second roll of plastic; g) while simultaneously unrolling said rolls of cathode/electrolyte laminate, anode laminate and first and second rolls of plastic, laminating said cathode/electrolyte laminate and said anode laminate together, between layers of said plastic sheet, whereby adjacent layers of plastic sheet/cathode/electrolyte/lithium anode/plastic sheet are in continuous mutual contact and extraneous air is excluded from between the layers, whereby a cylindrical laminated cell having first and second electrode edges is obtained; h) applying a current collector to each said edge; i) attaching leads to the respective current collectors; j) maintaining pressure on said laminated cell; and k) hermetically sealing said cell.
In some embodiments of the foregoing method the extruding step comprises extruding a uniform thin layer of the polymer electrolyte composition onto the cathode sheet in such a manner as to leave an uncovered margin of the substrate along one longitudinal edge of the substrate. The laminated cell may also be heated to improve the interface between the layers. The heating may be performed under reduced atmospheric pressure, or a vacuum, to further improve contact between the layers.
In yet another aspect of the invention, a method of making a thin film electrode/electrolyte half-element for a battery is provided. This method includes laminating together a sheet of thin film composite electrode and a sheet of thin film solid polymer electrolyte, to form a laminate. Optionally, the laminate is heated to improve contact between the layers, with the optional application of a vacuum to the laminate during the heating process. In some embodiments the composite electrode comprises a 0.1-100xcexc thick polymeric composite layer overlying a 0.5-50xcexc thick flexible plastic substrate. The polymeric composite layer may comprise a mixture of active electrode material having an average particle size of less than 0.1 micron in diameter, a first base polymer material comprising at least one ionically conductive polymer and having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25 xc2x0 C. when combined with a metal salt. The polymeric composite also contains the metal salt, an inorganic filler having an average particle size less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and an ionic conducting material having an average particle size less than 0.1 micron in diameter and an initial ionic conductivity of at least 1xc3x9710xe2x88x923 S/cm at 25xc2x0 C. In this embodiment, the solid polymer electrolyte has a conductivity greater than 1xc3x9710xe2x88x924 S/cm at 25xc2x0 C. or below and comprises a mixture of a second base polymer material comprising at least one ionically conductive polymer and having an initial conductivity of at least about 1xc3x9710xe2x88x925 S/cm at 25xc2x0 C. when combined with the metal salt. The solid polymer electrolyte mixture also contains the metal salt, an inorganic filler having an average particle size less than 0.05 micron in diameter and a surface area of at least about 100 m2/g, and an ionic conducting material having an average particle size less than 0.1 micron in diameter and an initial ionic conductivity of at least 2xc3x9710xe2x88x923 S/cm at 25xc2x0 C. The first and second base polymer materials may be the same or different polymers or polymer blends. In some embodiments, the polymer electrolyte is already in a cured and extruded form and in a roll, and the electrode/electrolyte are laminated together in a roll-to-roll manner. These and other embodiments, features and advantages of the present invention will become apparent with reference to the following description and drawings.